Study On Relationship Between Bisphenol-A Content And Aging Degree Of Polycarbonate Used As Food And Packaging Materials

The present work was concerned with the study about thermal-oxidative aging,photo-oxidation aging and exposuring to media aging of Polycarbonate used as foodand packaging materials in the hot air aging oven, anti-yellowing aging oven andmedia immersion system respectively. The main purpose was to investigate the effectof aging time on BPA content, structures, surface properties, optical properties andthermal stability of PC. In addition, the relationship between the BPA content andaging degree of PC was established preliminarily.PC in different thermal-oxidative aging time were characterized by GC-MS, FTIR,TG, UV-Vis spectrometer and stereo-microscope. It was indicated that BPA contentincreased first and then decreased with the increasing of thermal-oxidative aging time.The highest BPA content was495mg/kg, which was far beyond theGB/T5009.99-2003standard. Modification laws of phenolic hydroxyl absorptionintensity in IR spectra and the maximum absorption wavelength red shift of benzene inUV-Vis spectra were basically the same as that of BPA content; Initial weight losstemperature and maximum weight loss rate temperature of PC after thermal-oxidativeaging were reduced by1-2°C and3-5°C respectively, and the thermal stabilityreduced; Thermal-oxidative aging can induce the emergence of the surface crazing.Similarly to thermal-oxidative aging means, PC in different photo-oxidation agingtime were characterized by GC-MS, FTIR, TG, UV-Vis spectrometer. It was indicatedthat BPA content increased first and then decreased with the increasing ofphoto-oxidation aging time. It was showed that results by means of photo-oxidationaging were different from those of thermal-oxidative aging. BPA content afterphoto-oxidation aging was3-6.4mg/kg, which met the GB/T5009.99-2003standardbasically; Initial weight loss temperature and maximum weight loss rate temprature of PC after photo-oxidation aging were reduced slightly；Yellowness Index (YI), colordifference (ΔC) increased significantly. And the maximum amount can be increased bysix times and eight times respectively. Transparency (T) was decreased. The effect ofdifferent medium system on BPA content was investigated preliminary. It turned out tobe that BPA content was the more in acetic medium (348mg/kg) than in ethanol (26mg/kg) and water (38mg/kg) medium.In addition, influence of the sample preparation temperature on the PC propertieswas investigated. It was indicated that BPA content was3mg/kg before PC samplepreparation process, and BPA content was rapidly increased to266.4mg/kg after200°C PC sample preparation process. Initial weight loss temperature and maximumweight loss rate temperature of PC were decreased by14.9°C and5.8°C respectivelyafter200°C PC sample preparation process. IR, UV-Vis spectrum metrodcharacterization showed that BPA content and red-shift degree increased more whensample preparation temperature was230°C than when sample preparation temperaturewas200°C. It was indicated that the molding temperature of PC should be as low aspossible.